1. Field of the Invention
The present invention relates to a phonation valve for a breathing tube such as a tracheostomy tube.
2. Description of the Background Art
Phonation valves permit speaking by a patient having a breathing tube inserted into the patient""s airway, such as a tracheostomy tube inserted into a patient""s trachea.
Various valves for tracheostomy tubes are known in the art, including those disclosed in U.S. Pat. Nos. 3,137,299, 4,040,428, 4,325,366, 4,759,356, 4,971,054 and 5,259,378.
Phonation valves such as disclosed in U.S. Pat. No. 3,137,299 include a flapper-type valve diaphragm, which permits the patient to inhale through the valve, but closes on exhalation, thereby forcing air past the vocal cords and permitting the patient to speak.
Phonation valves with flat flapper-type valve diaphragms sometimes allow harmonic vibration noise during exhalation because of the natural vibration frequency of the diaphragm.
Harmonic vibration noise during exhalation resulting from natural vibration frequencies of the diaphragm can be reduced or eliminated by biasing the diaphragm against the valve seat. U.S. Pat. No. 4,759,356 discloses a phonation valve having a diaphragm which is biased toward the valve seat so that the valve diaphragm has a convex shape on the side of the diaphragm facing the valve seat. However, valves having diaphragms which are produced flat, and pre-loaded (biased) against the valve seat to prevent harmonic vibration during exhalation, can result in high cracking pressure to open the valve, with resulting uncomfortable breathing resistance for the patient.
There remains a need in the art for improvements in phonation valves.
In accordance with the present invention, a phonation valve which is cooperatively connectable to a breathing tube connected to a patient""s airway, comprises a valve body having first and second ends through which gas passes into and out of the valve. The first end is connectable to the breathing tube for passage of gas between the breathing tube and the valve. A valve seat is located within the valve body between the first and second ends. A thin, flexible diaphragm is provided, which is seated against the valve seat when the patient exhales. The diaphragm has comfort-improving structural features which may include: 1) a shape which is at least partly concave on a side of the diaphragm facing the seat, and/or 2) a web of substantially uniform thickness with a plurality of discrete areas of different thicknesses dispersed around the web, which are capable of damping resonance vibration of the diaphragm during breathing by the patient.